old2soon,
I could not figure out where to start measuring, or where to stop.
This is the best photo I could manage:

It would appear to me that the actual depth is not that critical, just so long as there is room enough to insert the slotted part.
IF you want to make an exact replica, I would be happy to ship you my center cover for you to measure, drool over, and otherwise have your way with, in exchange for your promise to return it when you are finished measuring, drooling, etc. If that is your desire, email me your address and I will ship first thing Monday. Email to vanagon [four] [zero] at gmail dot com.
That picture will do nicely thank you very much.

The reason i'm making my own tabs to replace the broken ones is right at $195.00.

Appreciate the offer of sending me the center section but i am reawakening old modeling skills from centuries past.

Thanks ever so much for everyones help.

When i get these installed and working correctly i'll try to fill people in on it.

So some cop food more caffeine and out to the shop!!

RIDE SAFE.